Continuing investigation into biochemical correlates and predictors of in vitro platelet preservation for transfusion confirms our earlier observation that pH does not predict in vitro platelet viability. Neither lipid nor selective amino acid feeding improves biochemical stability. A relationship is observed between glucose metabolism and lactate production; between phosphorolysis and platelet viabiliby, between LDH release and platelet viability; between donor dietary state and platelet viability and between gas exchange and platelet viability. Further, osmotic stress (present in all available transfusions models) is a reason for short in vitro platelet viability for transfusion. Finally, 25 degrees C appears to be superior to 4 degrees C for platelet storage.